Plastic blow-molded containers, particularly those molded of PET, have been utilized in hot fill applications where the container is filled with a liquid product heated to a temperature in excess of 180° F. (82° C.), capped immediately after filling, and allowed to cool to ambient temperatures. Plastic blow-molded containers have also been utilized in pasteurization and retort processes, where a filled and sealed container is subjected to thermal processing and is then cooled to ambient temperatures. Pasteurization and retort methods are frequently used for sterilizing solid or semi-solid food products, e.g., pickles and sauerkraut, which may be packed into the container along with a liquid at a temperature less than 82° C. (180° F.) and then heated, or the product placed in the container that is then filled with liquid, which may have been previously heated, and the entire contents subsequently heated to a higher temperature. Pasteurization and retort differ from hot-fill processing by including heating the contents of a filled container to a specified temperature, typically greater than 93° C. (200° F.), until the contents reach a specified temperature, for example 80° C. (175° F.), for a predetermined length of time. Retort processes also involve applying overpressure to the container. In each of these cases, the plastic containers are typically provided with vacuum absorption panels to accommodate volumetric changes in the container as the contents of the sealed container are heated and/or as the contents cool within the sealed container.
U.S. Pat. No. 6,439,413 issued to Prevot et al. and assigned to Graham Packaging Company, L.P. discloses a hot-fillable and retortable plastic wide-mouth blow-molded container having a sidewall with a pair of flex panels.
Co-pending U.S. patent application Ser. No. 10/129,885 filed on May 10, 2002 is the U.S. national phase of International Application No. PCT/USOO/31834 is assigned to Graham Packaging Company, L.P., and discloses a pasteurizable wide-mouth container having a novel base.
Other plastic wide-mouth containers having paneled sidewalls are disclosed in U.S. Pat. Nos. 5,887,739 issued to Prevot et al.; 5,261,544 issued to Weaver, Jr.; and 5,092,474 issued to Leigner. A pasteurizable plastic container having paneled sidewalls and a narrow neck finish is disclosed by U.S. Pat. No. 5,908,128 issued to Krislmakumar et al.
Containers having non-paneled sidewalls and yieldable endwall structures are disclosed in U.S. Pat. Nos. 4,642,968, 4,667,454 and 4,880,129 issued to McHenry et al.; 5,217,737 issued to Gygax et al.; 5,234,126 issued to Jonas et al.; 4,381,061 issued to Cerny et al.; 4,125,632 issued to Vosti et al.; and 3,409,167 issued to Blanchard. The above cited U.S. patents disclose containers having various base structures.
The structure of a so-called footed base is disclosed, in general, in U.S. Pat. Nos. 4,355,728 issued to Yoshino et al., 5,713,480 issued to Petre et al., 3,727,783 issued to Carmichael, 4,318,489 issued to Snyder et al., 5,133,468 issued to Brunson et al., 5,024,340 issued to Alberghini et al., 3,935,955 issued to Das, 4,892,205, 4,867,323 and Re. 35,140 issued to Powers et al., and 5,785,197 issued to Slat.
U.S. Pat. No. 4,321,483 issued to Dechenne et al. discloses a base having slightly angled annular surface and a central conical projection; and U.S. Pat. No. 4,386,701 issued to Galer discloses a blow molded plastic drum having a base which is designed to stack efficiently with the lid of a like drum.
Plastic containers, including those described in the above-mentioned references, containers, including containers designed for use in hot-fill processing. There remains a need to provide plastic containers that can withstand the rigors of pasteurization and retort processing in order to take advantage of the cost savings that can be realized through manufacture and recycling. The lighter weight of plastic containers as compared to glass can also advantageously reduce shipping costs.
Published International Application No. WO 02/02418 describes a container with a base that can be capable of withstanding the rigors of the pasteurization process. The base includes a large push up section formed with a sharp transition to the container sidewall. The base also must be heat set to a relatively high crystallinity.
While the above referenced containers and base structures may function satisfactorily for their intended purposes, there is a need for a plastic, wide-mouth, blow-molded container which is particularly suited for packaging a variety of viscous and other food products and which has a novel base structure that enables the container to be utilized in hot-fill, pasteurization and retort processes. The base structure should be capable of accommodating increased internal pressure experienced during pasteurization; capable of accommodating vacuum formed in the sealed container during cool down; and capable of resisting unwanted inversion, ovalization or like deformation. A container capable of efficient stacking with like containers is also desirable.